This invention relates to a method for monitoring the shape of the processed surfaces of semiconductor devices, and an equipment with a monitor for manufacturing such semiconductor devices.
In a process equipment for changing the shape of a processed surface, using chemical vapor deposition (CVD) and chemical mechanical polishing (CMP), etc., the condition of a processed surface, for example, the thickness of a thin film formed on the surface, is measured after the shape changing process.
FIG. 1 is a block diagram showing the structure of a measuring apparatus as the background art of the present invention.
As is shown in FIG. 1, a light source 101 emits incoherent light. The emitted light strikes upon a measurement point of the processed surface of a wafer 100 via a half mirror 102 and a lens 103. Then, the light reflects therefrom and enters a spectroscope 104 via the lens 103 and the half mirror 102. The spectroscope 104 divides the reflected light and emits light beams of different wavelengths to the pixels of a linear image sensor (one-dimensional CCD) 105. The linear image sensor 105 outputs, to a data processor 106, data on the intensities of the light beams of the pixels, i.e. the intensity of a light beam of each wavelength. The data processor 106 calculates the thickness of the wafer at the measurement point from the light intensity of each pixel. Thus, the thickness of the thin film formed on the processed surface can be measured.
However, when silicon dioxide is deposited on the to-be-processed surface of a wafer, which has a step, using, for example, a plasma-assisted CVD (P-CVD) tool, the resultant silicon dioxide film on the wafer has an uneven thickness. This is because a microscopic loading effect has occurred. This kind of thickness unevenness cannot be detected from the measurement of the thickness of only one portion of the wafer. Accordingly, even when the thickness of the measurement point is detected, it is difficult to feed the measurement result, as useful process control information, back to the actual process. The same can be said of any other film forming methods, as well as the P-CVD method.
A similar disadvantage to the above may also occur when the to-be-processed surface is etched or polished. For example, in reactive ion etching (RIE), trenching may occur, where a formed trench does not have a uniform depth. In CMP, dishing may occur, where the polished surface of the wafer is not uniformly flat.
Moreover, if in the case of a damascene process using CMP, a convex portion has an uneven surface, so-called "metal residue" occurs where a metal wiring material remains on a lower surface of the convex portion, thereby short-circuiting adjacent wires. To detect the "metal residue", inspection must be performed using an expensive low-throughput defect-inspecting device, or by the operator looking through an optical microscope. It is impossible during the inspection to subject the wafer to the next process, and hence a longer time and a greater manufacturing cost are required for the entire process.